1. Field of the Invention
The present invention relates to apparatus and methods for fabricating microelectronic packages. In particular, the present invention relates to microelectronic packages fabricated with a flex substrate and through silicon via technology.
2. State of the Art
Higher performance, reduced cost, increased miniaturization of integrated circuit components, and greater packaging densities of microelectronic devices are ongoing goals of the microelectronics industry. Moreover, small-sized, low-profile (thin) microelectronic packages are in high demand for use in small electronic devices, such as cell phones. Thus, the microelectronics industry fabricates a variety of small, thin packages.
FIG. 20 illustrates one such package known as a Wire Bonded Molded Matrix Array Package 200 (WB-MMAP). The WB-MMAP 200 comprises a microelectronic die 202 (such as a microprocessor, a chipset, a memory device, an ASIC, and the like) attached by its back surface 206 to a first surface 212 of a carrier substrate 208 (such as an interposer, a mother-board, a back surface of another microelectronic die, or the like). A plurality of bond wires 214 extend from bond pads (not shown) on an active surface 204 of the microelectronic die 202 to land pads (not shown) on the carrier substrate first surface 212 to make electrical contact therebetween, as will be understood by those skilled in the art. The carrier substrate 208 also includes a plurality of external contacts 218 attached to a second surface 216 thereof. These external contacts 218 connect the package to an external component (no shown), as will be understood to those skilled in the art. The microelectronic die 202 and bond wires 214 are encapsulated in a molding material 220 to prevent physical and chemical damage.
However, such packages are pad-limited, meaning that the microelectronic die 202 size (i.e., area) must be expanded (thereby wasting microelectronic die material) to allow sufficient bond pads to route signals to the carrier substrate 208. As bond wire 214 pitch is decreased to improve density, crosstalk issues between adjacent wires increase. Decreased bond wire 214 pitch may require the use of small diameter wires, which reduces current carrying capability, thereby increasing the need for more wires and defeating the purpose of tighter density.
Another known package, called a Flip Chip Molded Matrix Array Package (FC-MMAP), is illustrated in FIG. 21. The FC-MMAP 230 comprises a microelectronic die 232 (such as a microprocessor, a chipset, a memory device, an ASIC, and the like) attached by its active surface 234 to a first surface 236 of a carrier substrate 238 through a plurality of interconnects 242 (such as solder balls) extend from bond pads (not shown) on the microelectronic die active surface 234 to land pads (not shown) on the carrier substrate first surface 236 to make electrical contact therebetween, as will be understood by those skilled in the art. An underfill material 244 is dispersed between the microelectronic die active surface 234 and the carrier substrate first surface 236. The underfill material 244 provides mechanical support, contamination protection, and improves package reliability. The carrier substrate 238 also includes a plurality of external contacts 246 (such as solder balls) attached to a second surface 248 thereof. These external contacts 246 are used to connect the package to an external component (not shown), as will be understood to those skilled in the art. Unfortunately, such packages are also pad-limited, meaning that interconnect 242 pitch and/or routing limitations on the carrier substrate 238 prevent signal routing without increasing the size (i.e., area) of the microelectronic die 232.
A thin, stacked package configuration, known as a Folded Flex Ball Grid Array (FF-BGA), is illustrated in FIG. 22. A FF-BGA includes a flexible substrate to route electrical traces from the second microelectronic die to a position between the first microelectronic die and the carrier substrate to make electrical contact therewith. FIG. 22 shows an FF-BGA package 250, wherein a first microelectronic die 252 and a second microelectronic die 254 are attached to and in electrical contact with a first surface 258 of a flexible substrate 256 through wire bonds 262 and 264, respectively. The first microelectronic die 252 and second microelectronic die 254 may be fabricated in a manner discussed above with regard to the WB-MMAP 200 of FIG. 20. A first molding compound 266 and a second molding compound 268 is dispersed proximate each of the first and second microelectronic dice 252, 254, respectively.
The flexible substrate 256 includes conductive traces (not shown) disposed therein, thereon, and/or therethrough, which make contact with an array 274 of external interconnects 276 (such as solder balls) disposed on a second surface 272 of the flexible substrate 256 proximate the first microelectronic die 252. Thus, both the first microelectronic die 252 and the second microelectronic die 254 have external interconnects 276 within the array 274. The flexible substrate 256 is bent such that a back surface 282 of the first molding compound 266 can be attached to a back surface 284 of the second molding compound 268 with a layer of adhesive 286. The external interconnects 276 are attached to a substrate 288 using a standard solder ball attachment process, as will be understood to those skilled in the art.
Although such approaches result in serviceable microelectronic packages, it would be advantageous to fabricate microelectronic packages, which have increased signal routing without requiring an increase in the size of the microelectronic die.